Golem - the answer to all your Rayquaza prayers?
A decent team of R/SE Golem should be able to absorb anything Rayquaza has.
Articuno is double weakness against Ancient Power, not to mention glass cannon.
Honorable mention: Gyarados - might last 3 Ancient Power at the most, but it should get you some damage points with DT/O.
Answers
Golem will be a solid choice for sure
Don't agree about Articuno though. While it's true that it'll get destroyed by Ancient Power, double super-effective Ice damage is going to be too good to ignore, especially against the other two movesets. Hardly a glass cannon with it's high defense coupled with respectable stamina.
If he's released in time, then Aggron should also be a great option. Resistant to all of Ray's attacks, and can learn Dragon Tail and Stone Egde. Gardevoir should also be a strong choice because of the immunity to Dragon.
Golem is useable if you want TDO against AP movesets, but that's it. It loses to ice and Dragonite in DPS against all movesets and also loses in TDO to a bunch of mons against non-AP movesets.
Gyarados is just a worse Dragonite. Not worth using unless you don't have enough ice mons, Gardevoirs, Dragonites or Golems to fill the team.
Apparently according to pokebattler, it wants me to go in with 5 Dragonite (3 at 40, 2 at 35.5) and an Articuno (lvl 30, but not willing to spend rare candy on it). After that there's a Walrein, some Golem, my lvl 40 Raikou, and another Dragonite (not in that specific order) completing the top 12.
It's gonna save me some dust on ice types, as I checked what it would do if I boosted the Walrein and Articuno to 40, but it would not gain me enough for the dust investment.
At level 30 against DT/AP, Jynx, Piloswine, Lapras, Articuno, Dragonite and Walrein all rank higher than Golem due to having so much better DPS. Lapras in particular is almost strictly better than Golem, 1% less power, 70 seconds less time to win, but even all the others have 14% or more power, meaning you don't need Golem's better TDO if you're raiding with 7 or more people. Golem may be preferable if you're going with 5 players, but if the 4 others use Jynxes and rejoin once you'll be the only one getting only 2 damage balls.